The first known example of a slide rule coupled with time indication is attributed to Meyrat & Perdrizet (France – 1890).

Source: https://www.oughtred.org/jos/articles/Wyman_M&PB.pdf

Initially dedicated to scientists, the slide rule starts to democratize itself during the 1st World War.

It will be indeed largely used in aircraft cockpits, for marine navigation, for military calculations etc…

It is against that background that 3 Swiss watch manufacturers (MIMO, BREITLING & JUVENIA) will have the brilliant idea of making a wrist watch integrating a slide rule for ease of use by the modern gentleman.

The MIMO LOGA : Is it really the first wristwatch integrating a slide rule ?

MIMO watch manufacture (Manufacture International des Montres Or) presents in 1941 a 3 hands wristwatch integrating a slide rule made of 2 circular scales, one fixed (printed on the dial) and the other rotatable.

However, it is interesting to note that two patents (number 189 447 – 04/06/1936 by HOMIS Watch Co in Bienne and the number 204 559 – 25/04/1938 by Walter Moser in Berne) already describe the concept of integrating a slide rule into a wristwatch.

It clearly seems that the integration of a slide rule into a wristwatch is earlier than MIMO’s invention, but, the MIMO LOGA is anyway the first wristwatch integrating a slide rule to have been really produced and sold onto the market.

It appears that the LOGA was also produced under GIRARD PERREGAUX brand name after that GP was bought in 1928 by the owner of MIMO, Mr Otto GRAEF.

I have however never seen pics of this one and would love to hear from people who does !

BREITLING and the CHRONOMAT ref 769 :

Only few weeks after MIMO, Breitling applies for a patent in August, number 217 012, describing this time a slide rule having two scales with the outer scale having an anticlockwise read direction, which is different from the MIMO patent.

Moreover, the watch presented by Breitling in 1941 is a chronograph which makes it the first wrist chronograph with an integrated slide rule.

It is interesting to note that on the first ad showing the CHRONOMAT, what is supposed to be a patent number is written on the dial. However, it does not correspond to the good patent number (217 012) which will be correctly printed onto dials during the production run.

First ad showing the CHRONOMAT, dated from 1941Source : https://www.invenitetfecit.com/modeles/page-breitlingchronomat2.html

The JUVENIA ARITHMO :

JUVENIA is the third Swiss watch manufacturer to launch a wristwatch with a slide rule, this time in 1945.

The ARITHMO will be mainly produced under two versions :

A version with screwed caseback, called “Hermetic” as it was then waterproof, with a rotative besel in steel

Source: Menta Watches

A version with snap-on caseback and a pretty extraordinary glass, called “Refrascope”, because of a magnifier integrated into the outer edge of the glass to increase readability of the slide rule.

Source: Amsterdam Vintage Watches

Source: Amsterdam Vintage Watches

To be noted that first ARITHMO were not signed ARITHMO on the dial and that an automatic movement will be introduced in the 50’s.

Now that this short introduction is done, I guess we can move on to the watch I particularly love, the CHRONOMAT ref 769.

Detailed view of the Breitling CHRONOMAT ref 769:

Despite a first appearance in 1941 (see ad above), it is now admitted that the first appearance on the market was in 1942, under the reference 769.

As we can see on this ad above, the CHRONOMAT is described as the perfect watch for calculations in sports, economics etc…

Well, it is then what we call today a smart watch…

The CHRONOMAT 769 will be produced under many variations (dial, hands, case etc..) having the following characteristics :

Dial :

The dial of first 769 execution has arabic numerals (applied, lumed or painted) with a red telemeter in its center.

The patent number 217 012 preceded by the Swiss cross is written horizontally and in the center of the telemeter.

The dial is always signed Breitling Chronomat, without any logo or Geneve mention. Those two features will be on execution 2 dials though.

Also, a red arrow is printed on the dial between 5 and 6. To be noted that on the really first 769 (supposed to be from 1942), this arrow is not present.

It is also interesting to note that on early ads above, the arrow is not present.

Two subdials are present on the dial, one as a 45min counter and the other for the sweep second.

As for the red arrow, very early 769 don’t have 3,6,9 markers in the minute counter which appeared in the mid 40’s with the development of international calls and the need to materialize minutes of call.

Case and bezel:

Even if the chromed case is shown on catalogs after 1946, I have been told that none models with post 1946 serial numbers have surfaced so far. This makes this chromed case a pretty rare version then.

One particularity of the CHRONOMAT is its rotative bezel, protected by the patent number 217 012.

On very early versions, it seems that the besel is fitted with 3 screws while for later versions, the bezel is fitted by force onto the case.

stainless steel case with force mounted bezel

Pink gold case with bezel fitted by 3 screws

One difference between steel and gold cases is that lugs on the steel case are drilled while they are not on the gold case (see pics above).

Details of a pink gold case made by CARNAL & Cie

Note the little excrescence on the caseback to make it easy to open.

Very rare early chromed caseSource: @watchfred

Note that this interesting dial is showing the arrow between 5 and 6 but without 3,6,9 markers in the minute counter…

Hands:

Witnessing of the richness and the consistence of Breitling watches, and more generally of watch manufacturing back in the 40’s, different styles of hands were available depending of the dial and the case material.

As often, we see a consistence between case and hands metal. Also, a lumed dial will have lumed syringe hands while a painted of applied numerals dial will have straight baton hands (pink gold or blued steel).

Steel 769 with lumed dial and lumed syringe hands in blued steel

Pink gold 769 with applied numerals and pink gold baton hands

A special hands model was also available but, from what I know, only associated to the following dial version (named C) as visible on the extract of the Breitling catalog below :

Movement:

It is the Venus 175.

Different levels of finishing were available. Typically, gold cases had higher finishing level than steel cases.

Also, different bridge signatures were seen : from no signature on early models to Breitling signature after 1945/1946.

It has to be noted that many movements produced before 1945 were fitted in a case some years later. It is then not rare to find a CHRONOMAT with a post 1945 case but with a movement without any signature.

Venus 175 with BREITLING signature in capital letters

Venus 175 without any signature

We can see on the pic above that the inside caseback of gold cases are stamped by the Helvetia head, the mention 18K / 0,750 and a specific hallmark attributed to the case manufacturer, here 167 in a hammer’s head for the case manufacturer CARNAL & Cie.

CHRONOMAT 769 execution 1 variations (1942-late 40’s):

The first execution of the ref 769 was produced under many case/dial variations. Main dial options are illustrated in the extract of the 1946 catalog below :